How do you feel after a greasy, heavy meal—tired, sluggish, guilty? Did you know that the foods you eat can affect your overall energy level? You can keep your energy levels up all day simply by choosing the right foods and eating at the right times. Try eating for energy:

Drink plenty of water. Dehydration can make you feel fatigued. The right amount of water varies from person to person. Signs that you may not be getting enough water include frequent thirst, dark yellow urine, fatigue, mental fogginess, dry skin, and constipation. Avoid ice-cold water, which can slow digestion.

Don’t skip meals. Skipping meals can drain your energy reserves. Most nutritionists recommend five or six smaller meals spread throughout the day, but three regular meals with healthy snacks can work too. Find what works best for you and stick with it.

Reduce sugar and white flour. Foods like muffins, cookies, fruit juices, and white bread and pasta contain refined sugars and simple carbohydrates that can wreak havoc on blood sugar. This can lead to low energy. Try snacking on veggies, citrus fruits, nuts, salmon, dark chocolate, green and black teas and switch to whole grain or whole wheat breads and pastas.

Avoid energy drinks and bars. Many of these contain caffeine, which can increase your heart rate, make you jittery and lightheaded, and raise your blood pressure. Caffeine is also a diuretic, so it can lead to dehydration. Extra sugar can add unnecessary calories.

Eat within one hour of waking in the morning. This jump-starts your system and restores blood sugar levels, which can dip at night. A light, balanced snack an hour or two before bed can help you get a good night's sleep.

Eat protein for breakfast and lunch. Meat, eggs, fish, poultry, nuts, and seeds can give you extra energy. Put walnuts on your oatmeal rather than maple syrup or raisins. For afternoon energy, eat a lower carbohydrate, higher protein lunch. Avoid pasta-only meals.

Eat greens. Spinach, broccoli, kale, collard greens, mustard greens, and Swiss chard contain chlorophyll, magnesium, and B vitamins—all energy boosters!

Making these changes, in addition to getting regular exercise and a good night's sleep, can help keep you energized all day.